Known facilities comprise a bottom pipe more commonly known as a flow-line pipe, and an underwater riser pipe, often also referred to as a riser, for conveying the hydrocarbon from the sea bed where it leaves the flow-line pipe to the surface situated vertically above the sea bed.
Hydrocarbons are extracted from increasingly deep sea beds, on the one hand, and the underwater operating facilities are complex and require the use of a plurality of flow-line pipes and risers, on the other. These risers are also commonly referred to as hybrid towers. The difficulties lie in installing these underwater pipes from the surface. In particular, through this dense array of pipes it is awkward to connect a flow-line pipe with a riser.
Thus, the facility described in document EP 1 395 731 B, whereby the riser and the flow-line pipe are preconnected and transported thus as far as the installation site, is inappropriate because the riser/flow-line pipe assembly is submerged and then the riser is raised. It is therefore awkward to implement this method when other pipes are already in place, as these may become snagged during maneuvers.
Hence the idea has been developed of making the connection between the flow-line pipe and the riser in situ on the sea bed using underwater robots and inspection facilities that can be operated from the surface. Thus document FR 2 790 054 discloses a connection method and a facility for implementing it comprising an anchoring support installed on the sea bed and, in a first phase, an upstream end of the riser and a downstream end of the flow-line pipe are held through the anchoring support. The upstream end is equipped with a connector while the downstream end is equipped with a connection end piece. The connector and the connection end piece are then oriented toward one another in a direction extending vertically from the sea bed toward the surface. Next, to make the connection, the upstream end of the riser and the connector are driven translationally toward the connection end piece of the flow-line pipe so that the two pipes can be connected. Such a method of connection entails driving the connector translationally toward the connection end piece while at the same time controlling the vertical movement of the riser. In order to achieve this, a hauling cable is also used. However, the risks of the connector impacting on the elements of the anchoring support and of the connection end piece are high, given the masses that are thus being made to move.